System and method for controlling work machine

A system for controlling a work machine including a support portion operably supported by a vehicle body, a tilt rotator attached to a tip of the support portion, and an attachment having teeth and supported rotatably around three axes that intersect each other in different planes, by the support portion via the tilt rotator, wherein the tilt rotator includes a tilt portion and a rotation portion configured to rotate relative to the tilt portion, the system comprising:

• a processor,
• wherein the processor is configured to:
• acquire measurement values from a plurality of sensors,
• calculate a posture of the attachment with respect to the vehicle body based on the measurement values,
• determine a virtual rotation axis based on the calculated posture of the attachment,
• acquire an operation signal for operating the support portion from an operation device,
• generate a control signal for the tilt portion and the rotation portion of the tilt rotator to rotate the attachment around the virtual rotation axis so that an axial direction of the virtual rotation axis in a global coordinate system is held and a design surface and the teeth of the attachment are approximately parallel to each other, based on the calculated posture of the attachment and an operation amount indicated by the operation signal for operating the support portion, and
• output the generated control signal.